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ever wonder how pilots steer massive
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aircraft on the ground it's all thanks
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to the nose wheel steering system a
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critical part of ground control that
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ranges from simple to incredibly complex
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today we're taking a deep dive into how
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nose wheel steering works from light
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trainers to heavy jets let's roll
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most aircraft have a steerable nose
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wheel controlled from the cockpit this
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system allows the aircraft to be
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maneuvered safely and precisely while
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taxiing during takeoff runs and
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immediately after landing but not all
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aircraft use the same system some
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simpler planes rely on castering wheels
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and differential braking in small
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aircraft nose wheel steering is often
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achieved using a mechanical linkage
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connected to the rudder pedals when the
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pilot presses the pedals pushpull tubes
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transmit that motion to the nose wheel
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strut causing it to rotate left or right
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it's simple lightweight and highly
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effective for lighter aircraft when it
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comes to steering massive aircraft on
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the ground sheer muscle isn't enough
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these giants need precision and power
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and that's where hydraulic nose steering
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systems come into play
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most large aircraft are equipped with
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powered nose wheel steering because
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manual control just won't cut it and in
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almost every case the system relies on
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hydraulic power to get the job
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done while the designs might vary
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between aircraft they all share core
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components and principles the pilot
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controls steering from the flight deck
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typically using a tiller small wheel or
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even a joystick mounted on the side
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console or sidewall of the cockpit some
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aircraft even allow the system to be
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switched on or off depending on the
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phase of flight or maintenance needs
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that control input whether mechanical
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electrical or hydraulic is transmitted
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to a steering control unit which works
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like a metering valve this component
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routes pressurized hydraulic fluid to
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actuators that turn the nose wheel the
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actuators use a system of linkages to
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rotate the lower strut giving the
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aircraft precise directional control on
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many aircraft also connect the rudder
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pedals to the nose wheel for small
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steering adjustments especially useful
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during takeoff and landing when the
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fast the nose wheel steering tiller
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connects to a steering drum inside the
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flight deck pedestal as the tiller turns
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cables and pulleys send the motion to a
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control drum in the differential unit
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this moves a link to the metering valve
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shifting the selector valve and
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directing hydraulic power to turn the
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nose gear pressure from the aircraft
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hydraulic system is directed through the
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open safety shutff valve into a line
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leading to the metering valve the
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metering valve then routes the
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pressurized fluid out of port A through
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the right turn alternating line and into
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steering cylinder A this is a oneport
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cylinder and pressure forces the piston
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to begin extension since the rod of this
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piston connects to the nose steering
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spindle on the nose gear shock strut
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which pivots at point X the extension of
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the piston turns the steering spindle
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gradually toward the right as the nose
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wheel turns fluid is forced out of
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steering cylinder B through the left
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turn alternating line and into port B of
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the metering valve the metering valve
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directs this return fluid into a
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compensator that routes the fluid into
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the aircraft hydraulic system return
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when hydraulic pressure is applied the
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nose gear starts to turn but to avoid
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turning too far the system uses a
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follow-up linkage to control and stop
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the gear at the correct angle as the
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steering piston extends it turns the
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steering spindle on the back of the
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spindle are gear teeth that drive a gear
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on the orifice rod which rotates in the
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opposite direction this motion moves
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follow-up links on the nose strut
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turning a follow-up drum that drum sends
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movement through cables to a
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differential assembly which shifts the
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metering valve back to neutral stopping
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the gear at the right
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angle the compensator unit keeps
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pressure in the nose wheel steering
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cylinders at all times so they're always
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ready and act like shimmy dampers too
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inside the compensator is a
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spring-loaded piston and poppet valve
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one port vents air another connects to
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the metering valve return line and a
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third leads to the hydraulic return
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manifold when pressure hits 100 PSI the
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piston compresses the spring opening the
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puppet and allowing fluid to return this
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maintains a steady 100 PSI throughout
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the system keeping the steering
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cylinders pressurized and stable
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torque links on the nose gear help but
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they aren't enough to stop shimmy those
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fast unwanted vibrations during taxi or
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landing that's where the shimmy damper
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comes in it uses hydraulic damping to
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keep the nose wheel stable while some
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are built into the gear most are
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external units mounted between the upper
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and lower struts they work throughout
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all ground operations without
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interfering with steering thanks for
